Method and apparatus for endothermic reactions of organic compounds

ABSTRACT

The invention provides process and apparatus for conducting an endothermic reaction of an organic&#39; compound in the presence of molecular hydrogen and of multicomponent solids. The process comprises contacting the compound with a solid catalyst for the endothermic reaction and a hydrogen oxidizing solid reagent intermixed with the solid catalyst. Organic products of the endothermic reaction are produced, with evolution of molecular hydrogen. The solid catalyst becomes gradually deactivated by formation of carbonaceous deposits thereon. The evolved hydrogen undergoes an exothermic reaction with the hydrogen oxidizing solid reagent to form a reduction product which comprises deactivated hydrogen oxidizing solid reagent. The deactivated solid catalyst is reactivated by combustion of carbonaceous deposits thereon and the deactivated hydrogen oxidizing solid reagent is reactivated by contacting the reagent with an oxidizing agent in the absence of substantial quantities of hydrogen and in the absence of substantial quantities of organic compounds other than those on the surface of the reagent. One embodiment of the invention provides apparatus in which an endothermic reaction is carried out in the presence of a fluidized bed of catalyst and in the presence of particles of granular hydrogen oxidizing solid reagent which move downwardly through the fluidized catalyst bed, and in which the solid catalyst and solid reagent are separated prior to reactivation thereof in separate reactivation zones.

[0001] This application is a divisional of application Ser. No.08/278,782 filed Jul. 22, 1994, which is a continuation-in-part ofapplication Ser. No. 07/874,499 filed Apr. 27, 1992.

BACKGROUND AND PRIOR ART

[0002] Endothermic chemical conversions of hydrocarbons and otherreactants have been extensively practiced in the prior art. The largeinvestment capital requirements and operating costs associated with suchendothermic processes are often related to poor selectivity and lowconversion typical of those processes, or to the heat requirements ofthe processes. Such processes are usually ultimately limited inconversion by an unfavorable position of equilibrium. It is desirabletherefore to favorably change the equilibrium by continuous removal ofone of the reaction products, and to provide heat required for theprocess by the conduct of an exothermic reaction simultaneously with theendothermic reaction within the same reactor train. The presentinvention provides a selective process with improved conversion andconsequent lower installation and operating costs while also providingmajor benefits associated with in situ heat generation and equilibriumshift to achieve higher single-pass conversion.

[0003] Some of the commercially used endothermic processes of the priorart use adiabatic reactors, with the resulting disadvantage that therequisite reactor size to approach equilibrium conversion becomes quitelarge due, to the rapid deceleration of the reaction as the reactionmixture progresses through the bed of catalyst and the temperature dropswith increasing conversion of the reaction mixture. An isothermalreactor would require less volume to achieve an equivalent conversion.The present invention makes it possible to conduct endothermic reactionswhile avoiding the disadvantages of adiabatic reactors.

[0004] It has been proposed to conduct endothermic dehydrogenationprocesses in the presence of oxygen in order to react the hydrogenproduced in the dehydrogenation with oxygen to provide a continuousshift of the equilibrium to higher levels and to provide heat forendothermic reaction. However, a practical problem associated withendothermic processes which are conducted in the presence of oxygen inorder to oxidize: product hydrogen in situ is that introduction ofoxygen which has not been previously diluted with inert gas into thereactor may cause the production of oxygen-fuel mixtures within thebounds of the combustion envelope at temperatures above the autoignitiontemperature. This may lead to unselective combustion of desiredhydrocarbon products or to explosion in an extreme case.

[0005] To mix oxygen with hydrocarbons safely in a packed bed requires alarge expense. To avoid bulk mixing of oxygen and hydrocarbons, ahydrogen combustion catalyst in the form of a porous ceramic monolithhoneycomb, in which oxygen is diffused through the pores of the monolithand the hydrocarbon stream is passed through the tubular channels of thehoneycomb over a selective hydrogen combustion catalyst, might be used.In such a system, oxygen and hydrogen would not mix in the bulk exceptat the interface over the catalyst where selective combustion ofhydrogen occurs. This design ameliorates the safety concerns butintroduces a heat transfer problem. To effectively transfer heat fromthe hydrogen combustion zone into the catalyst beds in which theendothermic dehydrogenation reaction proceeds, high wall temperaturesare required which may exceed the temperature at which rapid thermalcoking of the feed occurs. This is a problem common to all thecommercial dehydrogenation processes which use a packed bed reactor fordehydrogenation and not just those which rely on in situ hydrogencombustion to provide heat. But even if hydrogen is oxidized in situ tomake the overall process thermoneutral, unless the exothermic combustionprocess can be conducted in the same zone as the endothermicdehydrogenation, heat transfer limitations may limit efficiency. Thepresent invention provides a way to avoid heat transfer problems whileachieving advantages of the use of a porous honeycomb catalyst whethersuch honeycomb catalyst is used or not.

[0006] Imai in U.S. Pat. Nos. 4,435,607 and 4,788,371 disclosesdehydrogenation of alkanes in processes which include selective hydrogencombustion by oxygen, but have the disadvantage of adding oxygen to azone in which there is either a high concentration of combustibleorganic compounds necessitating a high concentration of diluent such assteam to prevent combustion of organic compounds.

[0007] Clark et al U.S. Pat. No. 5,124,500 discloses a process for theremoval of hydrogen from a mixture of hydrogen and organic compounds byselective reaction of the hydrogen with a molecular sieve containing areducible metal cation, and discloses one type of material that could beused in the reactor design embodiment of the present invention. Nospecific reactor concept is disclosed by Clark, et al, nor any conceptof the importance or difficulty of efficiently using the exothermassociated with hydrogen oxidation to provide heat for thedehydrogenation.

DESCRIPTION OF THE INVENTION

[0008] The process according to the invention is a process forconducting an endothermic reaction of a liquid or vaporous organiccompound in the presence of molecular hydrogen and of multicomponentsolids including a solid catalyst for the endothermic reaction and ahydrogen oxidizing solid reagent to react with the hydrogen. The solidcatalyst and the hydrogen oxidizing solid reagent are intermixed, eitheras separate particles or incorporated within the same particle. Theorganic compound and the hydrogen are contacted with the catalyst andthe hydrogen oxidizing reagent under conditions to produce organicproducts of the endothermic reaction and to react hydrogen by anexothermic reaction with the hydrogen oxidizing reagent to formdeactivated hydrogen oxidizing reagent and water vapor. The deactivatedhydrogen oxidizing reagent is reactivated by contact with an oxidizingagent in the absence of substantial quantities of hydrogen and in theabsence of substantial quantities of organic compounds other than thoseon the surface of the deactivated reagent.

[0009] In one embodiment of the invention, the endothermic reaction is adehydrogenation reaction of an alkane to an olefin or of analkyl-substituted aromatic compound to an aromatic compound substitutedwith an unsaturated side chain. Preferably, the endothermic reaction isconducted in a fluidized bed and the solid granular hydrogen oxidizingreagent is passed downwardly onto the fluidized bed as raining solids.In one embodiment of the invention, hydrogen is cofed to the endothermicreaction zone with the hydrogen oxidizing reagent. The dehydrogenationis preferably conducted at a temperature in the range from about 500 toabout 700° C. and a pressure in the range from about 0 to about 100psig.

[0010] In one embodiment, deactivated catalyst and hydrogen oxidizingreagent are not separated prior to reactivating and are reactivated in acommon reactivation zone. In another embodiment, deactivated catalystand deactivated hydrogen oxidizing reagent are separated prior toreactivating and are reactivated in separate reactivation zones.

[0011] In one embodiment of the latter manner of conducting the process,the deactivated catalyst has lesser density or smaller size than thedeactivated hydrogen oxidizing reagent and the deactivated catalyst anddeactivated reagent pass from the endothermic reaction zone into aseparation zone. In the separation zone, a gravity separation iseffected, and deactivated catalyst is withdrawn from an upper portion ofthe separation zone and deactivated hydrogen oxidizing agent iswithdrawn from a lower portion of the separation zone.

[0012] In another embodiment wherein deactivated catalyst anddeactivated hydrogen oxidation reagent are separated prior toreactivation, the deactivated catalyst has different magnetic propertiesfrom the deactivated hydrogen oxidizing reagent and is separatedtherefrom by differentially attracting either the deactivated catalystor the deactivated reagent to a magnet.

Advantages of the Process of the Invention

[0013] The process of the invention has advantages over prior artprocesses for conducting endothermic reactions in that the process ofthe invention conducts the endothermic reaction in the same reactionzone in which an exothermic oxidation of hydrogen is conducted. Wherethe process of the invention is a dehydrogenation process, it has theadvantages, as compared with the process of Imai above, of lessexplosion hazard, greater selectivity for oxidation of only the hydrogencomponent rather than the hydrocarbon component, and elimination ofdilutes to control combustion of organics; and the advantages ascompared with Clark above, of providing improved reactor design whichefficiently uses the exotherm associated with hydrogen oxidation. Theinvention also provides novel processes using particular selectivehydrogen oxidizing agents.

Hydrogen Oxidizing Solid Reagent

[0014] In the dehydrogenation embodiment of the invention, organiccompounds are dehydrogenated in the presence of a selective andregenerable hydrogen oxidizing reagent which stoichiometrically, asopposed to catalytically, removes hydrogen as it is produced within adehydrogenation zone. No molecular oxygen is introduced into thedehydrogenation zone. The hydrogen oxidizing reagent functions as anoxygen transfer reagent, that is, as a reagent which transfers oxygenfrom the reagent to hydrogen, to form either water or a hydroxide, MOH,on the surface of the solid reagent, where the original reagent is MO.

[0015] Preferably the hydrogen oxidizing reagent used in the process ofthe invention has the formula MO_(x) where M comprises a metal selectedfrom the group consisting of iron, manganese, barium, calcium, samarium,praseodymium, ruthenium, tin, lead, germanium or bismuth, and where xvaries depending on the stoichiometry of the specific oxide. Examples ofsuch reagents are praseodymium oxides, barium peroxide, iron oxides,manganese oxides and samarium-calcium oxide mixtures.

[0016] The hydrogen oxidizing reagents include reducible metal oxides,metal complexes of organic ligands, or other inorganic compounds with orwithout metal atoms but which contain oxygen. These compounds arerelatively inert under dehydrogenation reaction conditions and can bereactivated with a source of oxygen. The reactivation conditions arechosen so as not to destroy the organic ligands, if they are present.Among the useful compositions are those metal oxides and doped metaloxides which promote the dehydrodimerization of methane, and which arereadily reducible by hydrogen but not as easily reducible byhydrocarbons as by hydrogen. The choice of hydrogen oxidizing reagentdepends in part on the nature of the hydrocarbon feed to bedehydrogenated and on the products thereof, and on the reaction andreoxidation conditions. Supported or unsupported iron, manganese andpraseodymium oxides and salmarium-calcium oxide mixtures are usefulhydrogen oxidizing reagents at conditions typically useful to convertisobutane to isobutene. Iron oxide in the form of magnetite is usuallypreferred to hematite. For lower temperature operation, compounds suchas supported cis-dioxo-bis-octafluorobipyridin ruthenium (VI)tetrafluoroborate may be a useful reagent. Other reagents as describedin the literature of methane coupling, such as disclosed for example inB. D. Sokolovskii, Catalysis Today, 14 (1992) 331, are useful ashydrogen oxidizing reagents according to the invention, as well as tinphosphate and tin pyrophosphate and the corresponding lead, germanium orbismuth phosphate compounds.

Use of Hydrogen Oxidizing Solid Reagents

[0017] The hydrogen oxidizing solid reagents used in the process of theinvention are those compounds and compositions which selectively reactwith hydrogen in admixture with hydrocarbons, and which can bereactivated by reoxidation. The reagents are readily reduced bydihydrogen but not by the organic compounds which comprise the feed ordehydrogenated organic products under the process conditions. Water canbe formed either as a direct result of the reaction between hydrogen andthe reagent, equations (3) and (4), while the hydrogen oxidizing reagentis in the reaction zone where hydrogen is produced by dehydrogenation,or in a second step as the reagent is oxidized, equations (1) and (2),in a reactivation zone in a step subsequent to the initial reaction withhydrogen:

2 MO+H ₂ --->2 MOH+heat (dehydrogenation zone)  (1)

2 MOH+{fraction (1/2)} O ₂--->2 MO+H ₂O+heat (reactivation zone)  (2)

or

MO+H ₂ --->M+H ₂O+heat (dehydrogenation zone)

M+{fraction (1/2)} O ₂ --->MO+heat (reactivation zone) Y

[0018] In reaction (1), the hydrogen oxidizing reagent, MO, is reducedby H2 generated in the dehydrogenation reaction to form MOH, and inreaction (2), MO is reactivated by oxidation of MOH. In reaction (3), MOis reduced by H₂ to produce a reduced form of the reagent, M, and inreaction (3), M is reoxidized to MO. In reaction (2), water is formed asa product of the reoxidation of MOH to MO. In reaction (3), water isformed as a product of the reduction of MO to M.

Dehydrogenation Catalysts

[0019] Dehydrogenation catalysts which may be used in the process of theinvention include catalysts known in the art for such reactions, andcatalysts which are the subject of related inventions. Prior artdehydrogenation catalysts include chromium supported on alumina, thecatalysts disclosed in Miller U.S. Pat. No. 4,726,216, the Pt, tin,cesium and alumina catalyst disclosed in Imai et al U.S. Pat. No.4,788,371, the dehydrogenation catalysts disclosed in Miller U.S. Pat.No. 4,726,216 and in Herber U.S. Pat. No. 4,806,624, potassium promotediron catalyst as disclosed in Imai et al, The Principle of Styro Plus,AICHE Nat. Mtg. New Orleans, March 1988, Reprint 64a; ProcessEngineering (London), (1988), 69, 17. When the reaction zone is afluidized bed, the dehydrogenation catalyst may be spray dried tofluidizable particle sizes, about 60-80 micron average particle size,and appropriate particle densities. Appropriate binders and texturalpromoters may be added as known in the art, to produce particles withsatisfactory physical properties once formed by spray drying.

Typical Embodiment of the Invention

[0020] In a typical embodiment of the process of the invention, adehydrogenatable hydrocarbon such as isobutane is contacted with a soliddehydrogenation catalyst such as nickel cesium alumina and with a solidhydrogen oxidizing reagent such as an iron oxide plus tin phosphatemixture under dehydrogenation conditions such as 600° C. and atmosphericpressure with space velocity GHSV of 885 hr⁻¹. The particles ofdehydrogenation catalyst are separate from the particles of hydrogenoxidizing reagent interspersed therein in a common reaction zone. Thehydrocarbon feed is dehydrogenated, forming an unsaturated hydrocarbonsuch as isobutylene, and hydrogen. The hydrogen reacts with the hydrogenoxidizing reagent, reducing components of the latter to a loweroxidation state, and forming water as a byproduct. Unsaturatedhydrocarbon is removed, as a product of the process and the reducedhydrogen oxidizing reagent particles are optionally separated from thedehydrogenation catalyst particles and removed to a hydrogen oxidizingreagent reactivation zone in which they are reoxidized to their formeroxidation state. The dehydrogenation catalyst particles are separatelytransported to a catalyst reactivation zone in which coke is burned offthe catalyst and then returned to the dehydrogenation reactor and mixedwith the reactivated hydrogen oxidizing reagent prior to contactinghydrocarbon feed to the dehydrogenation reaction. Optionally thedehydrogenation catalyst particles and the hydrogen oxidizing reagentparticles can be transported together to a common reactivation zonewithout prior separation.

[0021] Carbonaceous deposits form in the dehydrogenation reactor on boththe dehydrogenation catalyst and the hydrogen oxidizing reagent. Thecarbonaceous deposits on the hydrogen oxidizing reagent, and on anydehydrogenation catalyst that may be removed from the dehydrogenationreactor along with the hydrogen oxidizing reagent, are removed bycombustion during the reoxidation of the hydrogen removal reagent.

Separation of Dehydrogenation Catalyst and Hydrogen Oxidizing Reagent

[0022] In the dehydrogenation embodiment of the invention, the reactionis conducted with the dehydrogenation catalyst in a highly subdivided,or powdered, form, and the hydrogen removal reagent in the form oflarger and/or denser particles than the particles of the dehydrogenationcatalyst, and following the dehydrogenation and oxidation of theresulting hydrogen, a gravity separation is effected between the largerand/or denser hydrogen oxidizing reagent particles from the smallerand/or less dense particles of the dehydrogenation catalyst. The largerand/or denser phase from the separation is removed from the reactor forreoxidation as described above, and the smaller and/or less dense phasefrom the separation may be separately removed from the reactor.Alternatively, magnetic separation may be used to remove aniron-containing hydrogen oxidizing reagent from the dehydrogenationcatalyst. Cyclone separators may also be used to separate thedehydrogenation catalyst particles from the hydrogen oxidizing reagentparticles of a different particle size or density prior to separatereagent reactivation and catalyst reactivation steps of the process.

Reativation of Dehydrogenation Catalyst and Hydrogen Oxidizing Reagent

[0023] The dehydrogenation catalyst removed from the separation zone isreactivated in a dehydrogenation catalyst reactivation zone, in whichcarbonaceous deposits are burned from the dehydrogenation catalyst,under conditions which may be the same as or differ from those in thereactivation of the hydrogen oxidizing reagent. Any reduced hydrogenoxidizing reagent which may be carried into the dehydrogenation catalystreactivation zone with the dehydrogenation catalyst is reoxidizedtherein to its former oxidation state and relieved of carbonaceousdeposits thereon under the combustion conditions prevailing in thecatalyst reactivation zone. The conditions in the catalyst reactivationzone are those which are effective for reactivating a mixture ofdehydrogenation catalyst and hydrogen oxidizing reagent predominating indehydrogenation catalyst, whereas the conditions in the hydrogenoxidizing reagent reactivation zone are those which are effective forreoxidizing a mixture of hydrogen oxidizing reagent and dehydrogenationcatalyst predominating in hydrogen oxidizing reagent. The conditionsmaybe approximately the same in the catalyst reactivation zone and inthe reagent reactivation zone, and may even be conducted in the samereactivation zone, but it is preferred to conduct the catalystreactivation and reagent reactivation in separate zones under conditionsin each which are particularly effective for the catalyst reactivationand hydrogen oxidizing reagent reactivation respectively.

Process Heat

[0024] The reactivation of the hydrogen oxidizing reagent is conductedin a separate vessel or a separate zone from the zone in whichdehydrogenation and reaction of hydrogen with hydrogen oxidizing reagenttakes place. Heat may be generated both in the dehydrogenation zoneitself as a result of the initial reaction with hydrogen and in thereactivation zone. Heat produced in the latter case is transported bythe solid particles back to the dehydrogenation zone to help heatbalance the system. The amount of heat produced in the dehydrogenationzone can be throttled by adjusting the relative rate per unit reactorvolume of dehydrogenation relative to the rate of hydrogen burning, orheat can be removed by known heat transfer techniques. The hydrogenoxidation reactions are less sensitive to extremes of temperature thanthe dehydrogenation reactions. The relative rates of the respectivereactions are conveniently adjusted by varying the rate of introductionof the hydrogen removal reagent. In one embodiment of the invention,heat consumption by the endothermic dehydrogenation and heat productionby the exothermic hydrogen oxidation are balanced to achieve processthermoneutrality. In such cases when alkanes are the substrates fordehydrogenation to monoalkenes, roughly one half of the producedhydrogen is required to be oxidized to bring the system tothermoneutrality. The required amount of hydrogen burning is lessened tothe extent that usually undesired exothermic hydrogenolysis reactionsmay occur in the dehydrogenation zone. The hydrogen oxidizing reagentalso can be used advantageously without regard to the heat balance ofthe process. Even more hydrogen can be removed than dictated by the heatbalance requirements to facilitate further shifting of the position ofequilibrium toward products. Any excess heat produced in such case canbe removed by known heat transfer techniques and provided as a utilityto other processes.

[0025] The process of the invention provides high per-pass conversionsand in situ heat to the process by removing all or part of the producthydrogen as it is formed in the dehydrogenation zone. This is effectedby addition of a selective stoichiometric hydrogen oxidizing reagentwhich oxidizes the hydrogen exothermally to continuously shift thedehydrogenation equilibrium to a more favorable position andconsequently increase the limiting conversion of the process, and toprovide heat to offset the heat demand of the concurrent dehydrogenationreaction. Non-selective combustion of hydrocarbons and potentialexplosion hazards are avoided in the process of the invention, incontrast to processes in which molecular oxygen is introduced into thesame reactor as that which contains a high concentration of combustibleorganic compounds. In order to conduct the process of the invention in aheat balanced isothermal reactor, a circulating fluidized bed reactormay be used.

Particles Containing Granular Solids of Two or More Kinds

[0026] According to one embodiment of the invention, granular solids oftwo or more kinds are incorporated in particles containing solids ofeach kind. For example, for use in a dehydrogenation process, theparticles may contain both a dehydrogenation catalyst and a hydrogenoxidizing reagent. The dehydrogenation catalyst in the particles effectsdehydrogenation of the organic compound feed to the process. Thehydrogen oxidizing reagent in the particles reacts with hydrogenproduced in the dehydrogenation and is reduced to a lower oxidationstate. Carbonaceous deposits form on the particles as a result of thedehydrogenation conditions in the reactor, and these deposits areremoved by combustion in a separate reactivation zone in which theactivity of the dehydrogenation catalyst is at least partially restored,and the reduced hydrogen oxidizing reagent is simultaneously reoxidizedto a higher oxidation state under the conditions prevailing in thereactivation zone. The reactivated dehydrogenation catalyst and thereactivized hydrogen oxidizing reagent are returned to thedehydrogenation reactor to contact additional feed material. Thisembodiment is a particular instance of operation according to theinvention wherein the reactivation of the catalyst and the reactivationof the hydrogen oxidizing reagent are effected in a common reactivationzone. In the embodiments of the invention in which the dehydrogenationcatalyst particles are distinct from the hydrogen oxidizing reagentparticles, the reactivation of the catalyst and the reactivation of thehydrogen oxidizing reagent may be effected in the same reactivation zoneor in separate reactivation zones.

[0027] In a circulating fluidized bed system, with combustivereactivation of the dehydrogenation catalyst, one embodiment of theinvention provides a hydrogen oxidizing reagent which is capable ofreactivation together with the dehydrogenation catalyst. In anotherembodiment, a hydrogen oxidizing reagent is used which is reactivatedseparately from the dehydrogenation catalyst, for example because ofdisparate rates of regeneration of the two materials, or in order tostage the heat release during reactivation, or to decouple the cycletiming for the reactivation of the two materials; in this embodiment :araining solids fluidized bed reactor is provided which permitsseparation of the dehydrogenation catalyst component from the hydrogenoxidizing component, in order to allow for separate reactivation of thetwo materials. Where the lifetime of the dehydrogenation catalystbetween regenerations is relatively long, it may be desirable tocirculate the hydrogen oxidizing reagent to a separate reactivation zonemore frequently than the cycle time for reactivation of thedehydrogenation catalyst, or it may be necessary or desirable toreactivate the hydrogen oxidizing reagent under different reactivationconditions from the dehydrogenation catalyst reactivation conditions.

Raining Solids Circulating Fluidized Bed Reactor

[0028] A fluidized bed reactor operated in a nearly isothermal mode is apreferred reactor configuration for use in the process of the invention.In one embodiment of the invention, a circulating fluidized bed reactoris provided which contains a distribution mechanism to disperse asuperimposed free fall of granular solids comprising the hydrogenoxidizing reagent. Unlike the dehydrogenation catalyst, the freelyfalling solid is not fluidized by the fluidizing gas flow because thoseparticles are either larger or more dense than the fluidizabledehydrogenation catalyst particles. The freely falling particles whichcontain the hydrogen oxidizing reagent react with hydrogen as they fallthrough the dehydrogenation zone and collect at the bottom of thereaction vessel, and classification of the hydrogen oxidizing reagentfrom the dehydrogenation catalyst component is controlled. From thebottom of the reaction vessel, the now-spent hydrogen oxidizing reagentis circulated to a reactivator vessel for reoxidation in the presence ofan oxygen-containing gas and eventually recirculated to thedehydrogenation zone.

Applicability of the Invention

[0029] According to one embodiment of the invention, organic compoundsare dehydrogenated with the simultaneous selective conversion of atleast a portion of the byproduct dihydrogen to an oxidized product,either water or a reduced form of an added reagent such as MO inequations (1) and (3) above. Such operation is to be distinguished frommechanistically coupled oxidative dehydrogenation as discussed below.The invention potentially provides more favorable process economics thanthose of current commercially practiced processes. The invention may beadvantageously applied to new processes or to existing processes for thedehydrogenation of alkanes such as the Snam-Progetti-Yarsintez Process,which uses a fluidized bed reactor as used in one of the embodiments ofthis invention.

[0030] The process of the invention is applicable as a step in anydesired dehydrogenation reaction in which hydrogen is generated as aproduct and for which equilibrium does not lie substantially on the sideof products, or in any desired dehydrogenation reaction which consumesheat. Oxidative dehydrogenations in which molecular hydrogen is notgenerated as an intermediate in situ or as a final reaction product donot usually, but may sometimes, benefit. The process of the inventionmay be useful in dehydrogenation of alkanes to alkenes, alkadienes oralkynes such as the conversion of isobutane to isobutene or theconversion of ethyl benzene to styrene; the preparation of aldehydes orketones from alcohols; the preparation of alkanes or aromatics by thedehydrogenative coupling of lower alkanes or lower aromatics such as theconversion of methane to ethane or isobutane to2,2,3,3-tetramethylbutane or the conversion of benzene to biphenyl; theconversion of naphthenes (hydroaromatics) to aromatics such astetrahydronaphthalene to naphthalene; the cycloaromatization of alkanessuch as heptane to toluene when limited by equilibrium; thedehydrogenation of monoalkenes to dienes such as cis-butene-2 tobutadiene; and other processes for the preparation of intermediate orspecialty chemicals.

Apparatus for contactin Gas or Vapor with Granular Solids

[0031] The invention comprises in one embodiment apparatus forconducting an endothermic reaction of a fluid, that is, in vapor orliquid state, organic compound in the presence of molecular hydrogen andof multicomponent solids. The apparatus of the invention comprises (a)means for contacting the organic compound with a fluidized bed ofgranular solid particles of a catalyst for the endothermic reaction andwith granular solid particles of a hydrogen oxidizing reagent intermixedwith the fluidized bed, to produce fluid reaction products, deactivatedparticles of the catalyst having carbonaceous deposits thereon anddeactivated particles of the hydrogen oxidizing reagent, (b) means forseparating the particles of the catalyst from the particles of thereagent, and (c) means for separately reactivating the deactivatedparticles of the catalyst by combustion of the carbonaceous deposits andthe deactivated hydrogen oxidizing solid reagent by contact of thereagent with an oxidizing agent.

[0032] In one embodiment of the apparatus according to the invention,the means for separating catalyst from reagent comprise means foreffecting gravity separation of the particles of the reagent from theparticles of the catalyst. In another embodiment, the means forseparating comprise means for effecting magnetic separation of theparticles of the reagent from the particles of the catalyst.

The Drawing

[0033] The Figure illustrates a typical embodiment of process andapparatus according to the invention. Shown in the Figure is a catalyticdehydrogenation reactor 10, containing a fluidized bed 12 of fluidizablesolid dehydrogenation catalyst having about 60-80 micron averageparticle size, feed inlets 14 and 16, cyclone 18, product outlet 20,solids separation zone 22, hydrogen oxidizing reagent inlet 24, hydrogenoxidizing reagent outlet and transport line 26, transport gas inlet 28,reoxidation zone 30, air inlet 32, cooling jacket 34, steam inlet 36,steam outlet 38, reoxidized oxygen transfer reagent outlet 40, vapor andgas outlet 42, purge inlet 46 and distribution mechanism 48.

[0034] In operation, hydrogen oxidizing reagent, for example a compound,MO where M comprises a metal such as iron, circulates from reactor 10through transport line 26, reactivation zone 30, reactivated hydrogenoxidizing reagent outlet 40 from the reactivator, hydrogen oxidizingreagent inlet 24 to the reactor, and back through distribution mechanism48 into reactor 10, where it mixes with the fluidized dehydrogenationcatalyst in fluidized bed 12 and contacts, along with thedehydrogenation catalyst, a feed comprising hydrogen and hydrocarbon”for example isobutane, introduced through feed inlets 14 and 16. Thedehydrogenation catalyst catalyzes dehydrogenation of the feed, withgeneration of hydrogen, and the hydrogen oxidizing reagent reacts withhydrogen to form the compound MOH where M is a metal such as iron.Dehydrogenated product passes through cyclone 18, where catalystparticles are separated therefrom and returned to the catalyst bed 12,and is removed through product line 20. By gravity, the particles of thehydrogen oxidizing reagent, which are larger and/or denser than the“particles of the dehydrogenation catalyst, are concentrated in thelower portion of separation zone 22. In reoxidation zone 30, thehydrogen oxidizing reagent is contacted with air introduced through line32, which reacts with the MOH of the hydrogen oxidizing reagentparticles to form MO and water and generate heat. Some carbon dioxide isalso formed from carbonaceous material on the hydrogen oxidizingreagent. The water and carbon dioxide are removed, along with excessair, from reoxidation zone 30 through outlet 40.

The invention claimed is:
 1. An apparatus for conducting a continuousendothermic reaction of a fluid organic compound in the presence ofmolecular hydrogen and multi-component solids wherein saidmulti-component solids comprise a solid catalyst for said endothermicreaction and a hydrogen oxidizing solid reagent intermixed with saidsolid catalyst, said apparatus comprising: a first reactor forcontacting said compound with said multi-component solids to produceorganic products and deactivated multi-component solids; and at leastone second reactor in continuous sequence with said first reactor forreactivating said deactivated multi-component solids and circulating atleast one portion of said reactivated multi-component solids to saidfirst reactor for providing a continuous source of solid catalyst andhydrogen oxidizing solid reagent to sustain said endothermic reactionwithout interruption of the flow of said fluid organic compoundundergoing endothermic reaction and for providing a portion of heatrequired for said endothermic reaction.
 2. The apparatus of claim 1wherein said first reactor is a fluidized bed.
 3. The apparatus of claim1 further comprising a distribution mechanism near the top of said firstreactor for distributing said reactivated multi-component solids in saidfirst reactor.
 4. The apparatus of claim 1 wherein said hydrogenoxidizing solid reagent comprises reducible metal oxides.
 5. Theapparatus of claim 4 wherein said reducible metal oxides are selectedfrom the group consisting of iron oxides, manganese oxides, andsamarium-calcium oxide mixtures.
 6. The apparatus of claim 1 whereinsaid hydrogen oxidizing solid reagent comprisescis-dioxo-octafuorobipyridin ruthenium (VI) tetrafluoroborate.
 7. Theapparatus of claim 1 wherein said hydrogen oxidizing solid reagent isselected from the group consisting of tin, lead, germanium and bismuthphosphates or pyrophosphates.
 8. The apparatus of claim 1 furthercomprising at least one separator for separating and removing saiddeactivated multi-component solids from said first reactor.
 9. Theapparatus of claim 8 wherein said separation comprises gravity,magnetic, and cyclone separation.
 10. The apparatus of claim 1 whereinsaid at least one second reactor comprises two reactors for reactivatingsaid solid catalyst and said hydrogen oxidizing solid reagent.
 11. Theapparatus of claim 1 wherein said solid catalyst and said hydrogenoxidizing solid reagent are incorporated into single solid particles toform said multi-component solids.
 12. An apparatus for conducting acontinuous endothermic reaction of a fluid organic compound in thepresence of molecular hydrogen and multi-component solids wherein saidmulti-component solids comprise a solid catalyst for said endothermicreaction and a hydrogen oxidizing solid reagent incorporated into singlesolid particles, said apparatus comprising: a first reactor forcontacting said compound with said multi-component solids, to produceorganic products and deactivated multi-component solids; and a secondreactor in continuous sequence with said first reactor for reactivatingsaid deactivated multi-component solids and circulating at least oneportion of said reactivated multi-component solids to said first reactorfor providing a continuous source of solid catalyst and hydrogenoxidizing solid reagent to sustain said endothermic reaction withoutinterruption of the flow of said fluid organic compound undergoingendothermic reaction and for providing a portion of heat required forsaid endothermic reaction.
 13. The apparatus of claim 12 wherein saidfirst reactor is a fluidized bed.
 14. The apparatus of claim 12 whereinsaid hydrogen oxidizing solid reagent comprises reducible metal oxides.15. The apparatus of claim 14 wherein said reducible metal oxides areselected from the group consisting of iron oxides, manganese oxides, andsamarium-calcium oxide mixtures.
 16. The apparatus of claim 12 whereinsaid hydrogen oxidizing solid reagent comprisescis-dioxo-octafuorobipyridin ruthenium (VI) tetrafluoroborate.
 17. Theapparatus of claim 12 wherein said hydrogen oxidizing solid reagent isselected from the group consisting of tin, lead, germanium and bismuthphosphates or pyrophosphates.
 18. An apparatus for conducting anendothermic reaction of a fluid organic compound in the presence ofmolecular hydrogen and of multi-component solids which comprises (a)contacting said compound with a solid catalyst for said endothermicreaction and a hydrogen oxidizing solid reagent intermixed with saidsolid catalyst, thereby (i) to produce organic products of saidendothermic reaction and molecular hydrogen, (ii) to form deactivatedsolid catalyst having carbonaceous deposits thereupon, (iii) to reactsaid hydrogen by an exothermic reaction with said hydrogen oxidizingsolid reagent and (iv) to form a reduction product comprisingdeactivated hydrogen oxidizing solid reagent, (b) reactivating saiddeactivated solid catalyst by combustion of said carbonaceous depositsand (c) reactivating said deactivated hydrogen oxidizing solid reagentby contacting said reagent with an oxidizing agent in the absence ofsubstantial quantities of hydrogen and in the absence of substantialquantities of organic compounds other than those on the surface of thereagent, said apparatus comprising: a first reactor comprising afluidized bed reactor for contacting said compound with saidmulti-component solids which comprise said solid catalyst and saidhydrogen oxidizing solid reagent and wherein said multi-component solidsform an intermixed bed of particles for said endothermic reaction toproduce said organic products, said deactivated solid catalyst, and saiddeactivated hydrogen oxidizing solid reagent; and at least one secondreactor in continuous sequence with said first reactor for reactivatingsaid deactivated solid catalyst and said deactivated hydrogen oxidizingsolid reagent and circulating said reactivated solid catalyst and saidreactivated hydrogen oxidizing solid reagent to said first reactor forproviding a continuous source of active solid catalyst and hydrogenoxidizing reagent solid to sustain said endothermic reaction withoutinterruption of the flow of said fluid organic compound undergoingendothermic reaction and for providing a portion of heat required forsaid endothermic reaction.
 19. The apparatus of claim 18 furthercomprising a distribution mechanism near the top of said first reactorfor distributing said reactivated solid catalyst and said reactivatedhydrogen oxidizing solid reagent in said first reactor.
 20. Theapparatus of claim 18 wherein said hydrogen oxidizing solid reagentcomprises reducible metal oxides.
 21. The apparatus of claim 20 whereinsaid reducible metal oxides are selected from the group consisting ofiron oxides, manganese oxides, and samarium-calcium oxide mixtures. 22.The apparatus of claim 18 wherein said hydrogen oxidizing solid reagentcomprises cis-dioxo-octafuorobipyridin ruthenium (VI) tetrafluoroborate.23. The apparatus of claim 18 wherein said hydrogen oxidizing solidreagent is selected from the group consisting of tin, lead, germaniumand bismuth phosphates or pyrophosphates.
 24. The apparatus of claim 18further comprising at least one separator for separating and removingsaid deactivated solid catalyst and said deactivated hydrogen oxidizingsolid reagent from said first reactor.
 25. The apparatus of claim 24wherein said separation comprises gravity, magnetic, and cycloneseparation.
 26. The apparatus of claim 18 wherein said at least onesecond reactor comprises two reactors for separately reactivating saiddeactivated solid catalyst and said deactivated hydrogen oxidizing solidreagent.
 27. The apparatus of claim 18 wherein said multi-componentsolids comprise said solid catalyst and said hydrogen oxidizing solidreagent incorporated into single solid particles.